Electronic components, for example printed circuit boards, of an electronic control unit normally need to be protected from the surrounding environment which could be dangerous for the normal functioning of the electronic components, for example due to the presence of pollutants, such as dust, water or oil. For this reason electronic components may be contained in the inner volume of a housing, which is sealed to prevent contact with the external environment.
Conventional housings for electronic control units comprise a main body and a cover which are joined together along a border. Along the border area of contact between the main body and the cover, the housing comprises a sealing element, for example constituted by a gasket, an O-ring or a viscous dispensed material. The sealing element prevents pollutants, such as dust, water or oil from entering the housing through the border area.
The housing is normally subject to temperature variations, due to both self-heating of the electronic control unit and to variations in the climate conditions of the external environment. Accelerated tests to which electronic control units are subjected create even harsher temperature conditions. Differences in temperature between the sealed inner volume of the housing and the external environment may in turn cause pressure differences between a gas inside the housing and the ambient atmosphere surrounding the housing.
Due to differences in the coefficients of thermal expansion of the main body and of the cover and to positive or negative differences between internal and external pressure (overpressure or under-pressure, respectively), the housing is subject to mechanical stress. Such stress may cause deformation of the parts, in particular the cover, which are thinner in comparison with other parts, in particular the main body. As a result, this may cause stress on the sealing element between the main body and the cover, which may result into an adhesion or a cohesion sealant failure.